Democrats are aiming to rein in the White House's power to wiretap without a warrant and assert "state secrecy" in key court battles.

As Congress broke for a two-week recess last Friday, President Bush warned that the latest House version of the surveillance bill would "undermine America's security."

"This bill is unwise. The House leaders know that the Senate will not pass it. And even if the Senate did pass it, they know I will veto it," he said.

But Democrats are convinced that the public mood has shifted since August, when bipartisan majorities in both the House and Senate passed temporary changes in the Foreign Intelligence Surveillance Act (FISA) that the White House said were necessary to defend America against terrorists. That law expired Feb. 16.

At the heart of the dispute now is whether to grant retroactive immunity to telecommunications companies now facing lawsuits over their cooperation in warrantless surveillance.

The Bush administration argues that liability protection is crucial to national security. Facing multibillion-dollar class- action suits, telecommunications companies will be less willing to cooperate in antiterrorist surveillance, say top officials.

A Senate version of the bill, negotiated with the White House, includes retroactive immunity for telecoms. It passed by a bipartisan vote of 68 to 29 on Feb. 12.

The House bill proposes an alternative fix for telecom companies facing big lawsuits: to allow a judge to determine whether the executive branch's claim of the state secrets privilege is legitimate. It passed by a partisan vote of 213 to 197, with all Republicans and 12 Democrats voting in opposition.

"The telecoms have always had total immunity, as long as they get a statement from the administration. What's at issue is the administration's use of the state secrecy doctrine to prohibit them from using that immunity in court," says Rep. Jerrold Nadler (D) of New York, who proposed this strategy to the House Democratic leadership.

"A lot of our base voters are getting increasingly upset with Democrats having the appearance of caving on too many issues to the administration," says Nadler, who chairs the Constitution, Civil Rights, and Civil Liberties panel of the House Judiciary Committee.

Until recently, Democrats had assumed that a vote against the White House on an issue that Mr. Bush said was essential to national security could hurt freshmen Democrats in marginal districts. But at a recent House Democratic caucus meeting, several freshmen said they could explain this vote to their constituents, and cited recent polls backing that view.